I am traveling to Didcot this week. I am taking train from London and arriving at Didcot very late at night (around 10-11 PM). I want to go to the Harwell campus. There is no public transport available to Harwell after 10 PM (earliest after this is at 6.04 AM). Will I be able to get taxi or cab at Didcot Parkway station? I checked Uber but it is always showing no cabs available between given places. I found some taxi services on-line where I can pre-book them but I am not sure about their authenticity or whether they work such late night.
You should have no difficulty getting a cab from a railway station the size of Didcot. If there are none at the taxi rank, phoning any of the minicab companies in Didcot (there seem to be several) will quickly get you a cab. Pretty much any cab company in the UK will work 24hrs and 10–11pm isn't particularly late: any company will surely be operating at that time, since the pubs don't close until 11pm or later, and that's a significant source of income for cab companies. You could pre-book; if you call a cab when you get there, I doubt you'd have to wait more than ten minutes. I probably wouldn't pre-book because then I wouldn't be worrying about missing my train.
I doubt there are taxi scams in Didcot – it's just not a big enough place for that to be worthwhile. I live in Oxford (about 15km to the north) and, while I've never taken a cab from Didcot Parkway, I'd have no hesitation doing as I describe above, in basically any British town.
I've done this myself, many times. That late at night, I'd definitely pre-book; I've arrived at Didcot Parkway after 10pm on a freezing cold Sunday only to find no taxis outside and half an hour to wait even after phoning several companies. Other days, there's been a line of cabs waiting but it seems quite random.
The people I visit at Harwell usually book me with Pryors: https://pryors.co.uk/ Yes they have very nice cars and use words like "chauffeur driven Mercedes", but for a run like that you'll be on the meter and pay the same as any other taxi. They've never let me down and I'd recommend them whole-heartedly.
There is a taxi rank at Didcot Parkway. There have been occasions when none have been around at that time of night, but there is a good chance you'll find one right away. If not, the town has several reputable firms whose cars will tend to use this rank if they are available, but if not, their dispatch office is sure to be open for you to call. Booking ahead with one of them is probably prudent if you know when you will arrive.
Source: I live in Didcot.
Pryors is the biggest taxi company in Didcot. They're not the cheapest...but they're the ones with the poshest fleet (everything Mercedes). Their office is about ten minutes walk from Didcot Parkway station / a few minutes drive away. It's possibly worth booking with them (or another taxi company) if you can because at that time of an evening (depending what day of the week) the rank is often empty as the taxis are busy shifting people to or from various evening venues. But if you're not in a hurry, book them when you get there if the rank is empty.
My step son has run a cross a few dodgy individuals running taxi service in the area... they tend to put their prices up if they think they can get away with it (double the meter rate late at night... more if you're drunk). I've never heard any complaints about Pryors.
The taxi rank is to the right when you walk out of the station (if you walk out the main doors) or straight ahead if you go out the side door.
AFAIK Uber doesn't operate in Oxfordshire.
Another Didcot resident here. Pryors is a decent choice, but just for completeness there is also "Go Green Taxis" which are common sight in Didcot and online at http://www.gogreentaxisltd.co.uk/didcot-taxi-service/